The following relates to the radiation detector arts, nuclear imaging arts, and related arts.
Radiation detectors for use in positron emission tomography (PET), single-photon emission computed tomography (SPECT), and other nuclear imaging techniques sometimes employ a combination of a scintillator crystal that converts a radiation particle (e.g. 511 keV gamma ray, in the case of PET imaging) to a burst of light (i.e. scintillation light) in conjunction with a light detector arranged to detect the scintillation light. In a radiation detector array, photomultiplier tubes (PMT's) have conventionally been used as the light detectors. However, solid state light detectors such as silicon photomultiplier (SiPM) devices have performance and compactness advantages. A SiPM employs a silicon avalanche photodiode (APD) as the sensing mechanism where the APD is operated in Geiger mode for PET and SPECT applications. SiPM detectors can be manufactured as a monolithic array on a silicon wafer or chip, along with interconnect traces and optional signal processing electronics. SiPM arrays can provide analog or digital outputs, and timestamp circuitry can be integrated with the monolithic array. Additionally or alternatively, signal processing circuitry can be disposed with the monolithic SiPM array (e.g. as part of the PET detector ring, or in the detector head of a gamma camera used in SPECT imaging) as separate integrated circuit (IC) chips mounted on a common or neighboring printed circuit board.
In nuclear imaging, a radiation particle absorption event is localized to the detecting radiation detector. For improved spatial resolution, a depth of interaction (DOI) algorithm can be applied to approximate the depth within the scintillator at which the radiation particle was absorbed. DOI techniques can improve resolution and reduce noise by correcting for parallax effects when the radiation particle path has a large component oriented along (i.e. parallel with) the face of the radiation detector.
Various improvements are disclosed herein.
According to one aspect, a scintillator element includes N scintillator blocks of thickness t arranged to form an array of thickness t, and transparent or translucent material disposed between adjacent scintillator blocks of the array. The transparent or translucent material may comprise epoxy or glue disposed between adjacent scintillator blocks of the array and adhering the adjacent scintillator blocks together. Preferably, no reflective or opaque material is disposed between adjacent scintillator blocks of the array. In some embodiments the N scintillator blocks of the array are capable of generating scintillation light responsive to absorption of a radiation particle and have a refractive index for the scintillation light of at least n=1.8, and the transparent or translucent material disposed between adjacent scintillator blocks of the array has a refractive index for the scintillation light of at least n=1.6. By way of example, the N scintillator blocks may be N blocks of LSO, BGO, GSO, or LYSO. A reflective layer may be disposed on a top face of the scintillator element over all N scintillator blocks of the array, and an array of light detectors (e.g., an array of silicon photomultiplier detectors formed monolithically on a silicon substrate) may be disposed on a bottom face of the scintillator element and arranged to detect scintillation light generated in the scintillator element. For PET applications, the scintillator element and the array of light detectors define a radiation detector configured to detect 511 keV radiation.
According to another aspect, an imaging system includes a radiation detection component and an image reconstruction processor comprising an electronic data processing component configured to reconstruct an image from radiation data acquired by the radiation detection component. In this embodiment, the scintillator element and the array of light detectors define at least one radiation detector of the radiation detection component of the imaging system. In some embodiments, the imaging system is a PET imaging system or a SPECT imaging system. The imaging system may include a depth of interaction (DOI) processor comprising an electronic data processing component configured to estimate the depth over the thickness t of the scintillator element at which a radiation absorption event occurred based on detection by the array of radiation detectors of scintillation light generated in the scintillator element by the radiation absorption event. The imaging system may include a position processor comprising an electronic data processing component configured to locate a radiation absorption event based on detection by the array of radiation detectors of scintillation light generated in the scintillator element by the radiation absorption event. By way of example, the position processor may be configured to locate the radiation absorption event using Anger logic.
According to another aspect, a scintillator element is constructed by operations including: dicing a scintillator wafer or puck to generate scintillator blocks of thickness t; assembling N of the scintillator blocks of thickness t to form an array of thickness t; and disposing transparent or translucent material between adjacent scintillator blocks of the array. The transparent or translucent material may be a bonding material, and the disposing may comprise bonding adjacent scintillator blocks of the array together using the transparent or translucent bonding material. In another approach, the assembling may include bonding the N scintillator blocks to a common substrate, such as a monolithic array of SiPM light detectors. In some embodiments, the dicing operation generates at least 2N scintillator blocks and the assembling and disposing operations are repeated R times to construct R scintillator elements, where R is greater than or equal to two.
According to another aspect, a method comprises: generating scintillation light in a scintillator comprising N scintillator blocks bonded together to form an optically continuous scintillator element responsive to a radiation absorption event occurring in the optically continuous scintillator element; detecting the scintillation light using an array of light detectors; and locating the radiation absorption event in the optically continuous scintillator element based on the detected scintillation light, wherein the locating employs an algorithm treating the optically continuous scintillator element as an optically continuous light transfer medium. The locating may include applying a depth of interaction (DOI) algorithm to locate the radiation absorption event over a thickness t of the optically continuous scintillator element.
According to another aspect, an optically continuous scintillator element comprises N scintillator blocks bonded together to form an optically continuous light transfer medium. Preferably, no reflective or opaque material is disposed between adjacent scintillator blocks. In some embodiments the N scintillator blocks are N LSO, LYSO, BGO, or GSO scintillator blocks bonded together to form the optically continuous light transfer medium using a bonding material having a refractive index of at least 1.6 for scintillation light generated by absorption of radiation in the optically continuous scintillator element. In some embodiments the N scintillator blocks have refractive index of at least 1.8 for scintillation light generated by absorption of radiation in the optically continuous scintillator element, and the N scintillator blocks are bonded together to form the optically continuous light transfer medium using a bonding material having a refractive index of at least 1.6 for the scintillation light.
One advantage resides in providing increased yield in large-area scintillator crystal production.
Another advantage resides in providing higher quality large-area scintillators
Another advantage resides in reduced large-area scintillator production cost.
Another advantage resides in providing radiation detectors with improved resolution.
Another advantage resides in providing scintillator arrays for radiation detectors having larger active area.
Numerous additional advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description.